From f7da73e371bcb909a18e654918b5d1e7931e5652 Mon Sep 17 00:00:00 2001
From: Eric Wong <e@80x24.org>
Date: Tue, 3 Jan 2023 07:25:24 +0000
Subject: mymalloc: use ftruncate(2) when creating a sparse file

Unlike pwrite(2), it won't dirty the last page, and it's fewer
arguments so argument passing is simpler.
---
 mymalloc.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mymalloc.h b/mymalloc.h
index e781b43..eda669f 100644
--- a/mymalloc.h
+++ b/mymalloc.h
@@ -69,9 +69,9 @@ static void *my_mmap(size_t size)
 	if (fd < 0) {
 		flags |= MAP_ANONYMOUS;
 	} else {
-		ssize_t w = pwrite(fd, "", 1, size - 1); /* sparse file */
+		int t = ftruncate(fd, size); /* sparse file */
 
-		if (w <= 0) { /* 0 may be ENOSPC */
+		if (t < 0) {
 			flags |= MAP_ANONYMOUS;
 			close(fd);
 			fd = -1;
-- 
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